CVE-2026-71562 Erlang CVE debrief

Who should care

Erlang/OTP users and administrators should assess exposure and verify versions to prevent potential availability degradation from malicious HTTP servers. This includes reviewing and adjusting httpc configuration to limit potential impact, monitoring for unusual HTTP server responses and system performance, and verifying and updating Erlang/OTP versions to the latest patched versions.

Why it matters

CVE-2026-71562 is a medium-severity vulnerability in Erlang/OTP inets httpc that can cause availability issues if not properly patched and configured.

• Potential availability degradation from processing large numeric headers
• Verification of Erlang/OTP versions and httpc configuration is necessary
• Monitoring for unusual HTTP server responses and system performance is recommended

Technical summary

The Improper Validation of Specified Quantity in Input vulnerability in Erlang/OTP inets httpc allows a malicious or compromised HTTP server to degrade availability by returning a numeric header whose value is a very long run of digits. httpc_handler.erl converts the server-supplied Content-Length with list_to_integer/1 before comparing it against max_body_size, so the size check cannot protect the conversion, and the option defaults to nolimit in any case. The same unbounded conversion appears in httpc_response:format_response/1 for Content-Length and in httpc_response:get_ms_from_retry_after/1 for Retry-After, which is guarded only by a check that the first character is a digit.

Defensive priority

Defenders should prioritize verifying and updating Erlang/OTP versions to prevent potential availability degradation from malicious HTTP servers.

Recommended defensive actions

• Verify and update Erlang/OTP versions to the latest patched versions
• Review and adjust httpc configuration to limit potential impact
• Monitor for unusual HTTP server responses and system performance
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but the scope of affected versions and potential impact require further verification. The Improper Validation of Specified Quantity in Input vulnerability in Erlang/OTP inets httpc allows a malicious or compromised HTTP server to degrade availability by returning a numeric header whose value is a very long run of digits. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to in

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.